Each of known hybrid systems of this kind disclosed in Patent documents 1 and 2 includes a combination of a high-pressure fuel cell and a gas turbine for driving a generator.
Patent document 1: JP 8-45523 A (FIG. 1 and the specification)
Patent document 2: JP 10-12255 A (FIG. 1 and the specification)
The conventional hybrid system using a gas turbine combined with a compressor, and a high-pressure fuel cell that operates at a high pressure equal to or higher than the output pressure of the compressor has the following problems. A small hybrid system has a small gas turbine, and a fuel cell contained in a high-temperature, high-pressure container. Therefore, the hybrid system needs a protective device capable of properly carrying out a shutdown procedure and of discharging a high-temperature, high-pressure gas outside the system in an emergency. The protective device imposes a large cost load on the small hybrid system. The hybrid system needs a differential pressure control system and control techniques for limiting the variation of differential pressure during emergency shutdown within an allowable range determined on the basis of the structural strength of the fuel cell. The differential pressure control system also increases the cost of the hybrid system. The high-temperature, high-pressure container and the high-temperature, high-pressure pipes also increases the cost of the hybrid system.